I buy the Nam Pla brand of Thai sweet chili sauce but I am sure you can make it as well (just make a thick sugar syrup and add some roughly grinded arabol chilies to it along with some minced garlic and let it sit, it will not be identical to the bottle one but should work) I have made the version below numerous times and it comes out good.

You need to define what you mean by chili sauce--is this a hot paste made mostly of chilis, or a sweet, almost like ketchup, tomato-ey sauce for sandwhiches?

The Ball Blue Book has the ketchup-y recipe, and I will type it out for you, if that is what you want. (I use that recipe for a sweet/hot salsa, leaving out the cinnamon and cloves and adding more chilis.)

__________________I just haven't been the same since that house fell on my sister.